This application is related to those types of apparatus used in the conveying and cutting of sheet material, particularly fabric and other porous sheet material. The conventional method and apparatus for spreading and cutting multiple sheets of fabric has been to spread the sheets of fabric (as many as 300 plies) on a work table, stacking the sheets layer upon layer until the desired number of plies or sheets makes up the stack. When the stack is complete it is moved manually (generally by sliding) to a cutting station which is likely another area along the same work table. The spreading and stacking may be done manually or by spreading machines specially designed to spread, selectively cut, and stack the sheet layers. The movement of the stack, however, has traditionally been a completely manual procedure wherein several workmen, the number dependent upon the weight of the fabric stack, grip the sides of the stack and drag it to the cutting area. At the cutting area, the cutter operator must hold down the area of the stack immediately adjacent that which he is cutting to improve the quality and accuracy of the cut. Efforts to make the aforesaid process more efficient have generally been concentrated in the areas of the spreading apparatus and the cutting apparatus. Very little success has been obtained in the means for moving the fabric from one work station to another or in holding of the fabric in position during stacking and/or cutting.
While other industries have utilized air currents or air cushions for movement of heavy sheets of material into position, very little effort has been expended in utilizing the equipment which generates the air cushion to improving the spreading and cutting operations on fabric materials. Two U.S. patents, U.S. Pat. Nos. 3,670,612 and 3,253,756 are illustrative of approaches to using air cushions in the handling of sheet material. U.S. Pat. No. 3,253,756 is directed to a method and apparatus for conveying, scoring, and cutting sheets of glass. As such there is disclosed an air cushion for moving the glass from one work station to another work station. At the scoring and cutting station, the sheets of glass are held in place by cutting off the positive flow of air to eliminate the air cushion. After the air supply is shut off, the table top frictionally holds the glass sheet in position while a plurality of vacuum cups engage the upper surface of the glass sheet to further aid in holding it in place. The Johnson patent, U.S. Pat. No. 3,670,612, is directed to a card cutting apparatus wherein a single web or sheet of material is held in place by vacuum during a die cutting operation. After the cutting is completed the vacuum is released and air under a positive pressure is supplied to the work station to divert scrap material from between the cards into a waste receptacle and also to release the cards onto a conveyor for stacking.
Such air table apparatus has not been successful for use in the clothing manufacturing industry because the air pressure in such devices has generally been insufficient for moving heavy stacks of fabric from one work station to another. Further, the creation of a vacuum on the underside of a non-porous workpiece is not the same concept as drawing air through a plurality of porous sheets in a stack for holding large stacks of fabric securely in place during a cutting operation. Prior attempts to utilize suction for holding fabric stacks in place for cutting, such as those shown in U.S. Pat. No. 3,598,006, have involved the use of a vacuum chamber or manifold beneath the fabric guides, and other such elements for holding the fabric in alignment, in conjunction with an overlying sheet of air impervious material to aid in the creation of a vaccum to hold the fabric in place. Such apparatus is quite expensive to manufacture and the use of an overlying sheet or film creates problems with operators being able to follow a pattern unless the pattern is placed on top of the film material. If a pattern is placed on top of the film material, then the cutting knife must cut through the film, meaning that the film must be replaced with every cutting operation. If the pattern is printed on the film it creates further expense in pattern production.